Pressure alleviator



May 23, i933. p' B' E EWTTy Er AL 1,910,345

PRES SURE ALLEVIATOR Filed Feb. 27, 1928 to the apparatus.

Patented May 23, 1933 i UNITED STATES ears-Nrorties PERCY' B. LEVITT AND THOMAS S. BLAIR,v 0F JACKSON'HEIGHTSNEW YORK, ASSIGNDRS TO DOHERTY RESEARCH COMPANY, 0F NEVVVv YORK,` N. Y., A GORPORATXON' 0F DELA-i WARE rnnssunn lAIiLnvrA'ror-i Applicatie area February 27, resav .sei-iai nu. 25mm The-present invention relates tohigh pressure pumps having relief valves and more particularly to high pressure pumps form-l ing parts of fuel injection systems of internal combustion engines. f

lt has `been proposed to inject liquid fuel into the combustion chamber of an internal combustion engine under high pressure by means of a pump provided with a relief valve through which the liquid is discharged during the first portion and last portion of the forcing stroke of the pump plunger, the fuel being diverted to thc injection valve ofthe engine only during that portion of the stroke in which the pump plunger is moving at a very high velocity.

Fuel injection systems of the type just described have been used quite widely and it has been found convenient and desirable often to place the fuel storage chamber at a considerable distance from the pump bar'- rel. It has been found, however, that the inertia and friction of the column of oil re# turning to the long supply line from therelief valve have been such thatv the supply ofv fuel to the engine has failed, orthe oil pressure in the pump is not immediately released causing a dripping of' oil at the injection nozzle. l

It is the principal obj ect ofthe present inf vention to provide a means of avoidingrthe difficulties just mentioned. Y Q

According to the present inventiomthe supply of liquid to the pump is assured by connecting a pressure alleviatorrhavingan accumulator chamber tothe pipelineA leading from the relief valve to the supply linel i The pressure alleviator within the present invention may be in the form of an Aair chamber or of a mechanical accumulator. It has been found, however, that when an air cham'- ber is used in the location indicated theair in the air chamber is often dissolvedrin the oil so that the air chamber becomes lliquidbound and ceases to function. Thisdiiiiculty may of course, be 'avoided by injecting a small amount of air into the air 'chamber at 'suitable intervals. Howeven'this method of overcoming the diflculty adds complication Another object of the present invention is to providey a mechanical alleviator adapted to overcome the dil'flculties mentioned above. Further objects and advantages of the present invention will hereinafter appear.

yInthe accompanying drawing, I have illustrated speciiic embodiments of the present invention. v Insaid druving,l Fig. l is an elevation, somewhat diagrammatic in character, of an internalcombustion engine cylinder having an apparatus according to the present invention installed in connection therewith, parts being broken away and parts being shown in section for purposes of illustration. Fig. 2 is a'jvertica sectionof a pressure alleviator according to the present invention and appearing in Fig. l.

Fig.l 3 illustrates.ay modified formof the apparatus. y Y V Referringv to the drawing more in detail, 10 is the cylinder of aninternal combustion engine having an injection valve l2. Oil is supplied under Vpressure to the valve 12 by pipe 24a from a fuel pump provided witha working barrell li'lf Liquid fuel for use 1n the cylinder lll'mmayl bestored Aat any convenient point, a'suitable fuel receptacle being indicated diagrammatically in Fig. l at point 16. The fuel receptacle 16 is connected to an intake valvcalS of the fuel pump by the pipeline 2i() andthe outlet valve 22 of the fuel pumpis connected to the injection valve 12 pipeline `24. In, the pump barrel 1,4 is a p unger26 which may be` reciprocated by any desiredy vorV suitable means, l In the arrangement illustratemjphmger 26 is operated from the shaft 2,8 of` theengine by means, of. an eccentricf() and slde32, y j The pump vbarrel lei `is provided withk a relief valve fl'which is maintained open at the beginningand-near thev end of each stroke :of theplunger 26, but is permitted to close during that portion of the stroke of the lplunger 26 in 'which' it is traveling at its highest rate of speed. Any suitable or desired means may be used for opening relief 3.4 and permitting it tofclose at the desired instant. Inthe :arrangement illustrated the stem; 36 ofvalve'ga carries 'a Contact. head 38 which is actuated by the cams 40 and 42 to 0pei-ate the valve 34. Cams 40 and 42 moreover, are illustrated as being opera-ted from the eccentric 30 by means of a crank 44. When the valve 34 is open, fluid is free to flow from the pump barrel out through the overflow pipeline 46 back through pipe 47 topipe 20.

It will be understood that, in general, the arrangement heretofore described forms no part of the present invention and is not claimed herein. Connected into the overflow pipeline 46 is an alleviator 48. In the particular embodiment of the invention herein disclosed alleviator 48 includes a T 50 con-v nected intothe pipeline 46. As illustrated, the side port 52 of the T 50 connects with a passage 54 in a head 56, said head having a nipple 58 forming the wall of the passage 54. Mounted on the head 56 is a cylinder 60 within which is mounted for reciprocation a piston or plunger 62. The head 56, cylinder 60, and piston 62 form the walls of an accumulator chamber 64 connecting with the passage 54 and adapted to receive' liquid therefrom which has been discharged through relief valve 34, and to return the liquid so received from pipe 46 back to the pipe under certain conditions. The plunger 62 is normally forced toward the head 56 by a spring 66 so that the amount of liquid stored in chamber 64 normally tends toward a minimum. The spring 66 thrusts against the plunger 62 at one end and at its other end it thrusts against a collar 68 on a pin 7 0 fixed in a crossbar 72 supported Yfrom the head 56 by means of bolts 7 4, 74 or the like. Preferably, the plunger 62 is hollow so that the coil spring 66 may be of considerable length without increasing the overall height of the alleviator 48. Preferably lalso the cylinder 60 is provided with a stufling-'box 76 at its outer end forming a liquid-tight joint with the plunger V62.V

In the operation of the pressure alleviator above described, when relief valve 34 is opened, and the liquid is discharging through pipe 46, the pressure in this pipe tends to rise and the liquid to enter into the chamber 64. The pressure in chamber64 thereupon becomes high enough to lift the plunger 62 against the thrust of spring 66, permitting fluid to be stored temporarily in the chainber 64 which is returned afterward to the line 20 more gradually than would otherwise be the case, thereby permitting an even'flow of liquid inthe pipeline 2O to the intake valve 18 during the suction stroke of the piston 26 and preventing the` failure of fuelrequired by the engine. The insertion ofthe alleviator in pipe 46 y,removes the inertia effect of the .oil in the'pipeline 2O and allows of the rapid opening of valve 34 with the consequent quick closing of the pump outlet valve 22 andthe quick cutofi' of fuelvto the spray in- Jection nozzle. It will be evident, however,

that the flow of fluid through pipe 46 occurs in bursts or spurts. The quicker the valve 34 opens, the sharper are the bursts of liquid in pipe 46 and the harder to reestablish the liow in pipe v20 in the direction toward the fuel pump. It has been found to be desirable to make use of the kinetic energy of the fluid discharged from the relief valve 34 through pipe 46 by mechanically diverting the liquid 'into the passage 54 leading to the accumulator chamber 64. For this purpose, it is preferred to weld a deflecting member 78 to the inner surface of the T 50. As illustrated, deflector 78 is fixed to the head of T 50 substantially opposite the mouth of port 52 and passage 54. Preferably, however, the deflector 7 8 is placed somewhat toward the discharge side of the T from the center line of the port 52, passage 54 and cylinder 60. Preferably, the deflector 7 8 is curved so as to present concave surfaces 80, 80 to the port of the inlet and outlet of the passage through the head of T 50. The deflector 78, moreover, is formed into a thin point or tip 82, adapted to divert the liquid toward the discharge end of the T 50 when the liquid is flowing out of chamber 64 without causing eddies, or the like, which reduce the efficiency of -the apparatus.

It has been found preferable, moreover, to. provide a boss 84 on the inner face of the plunger 62, said boss having a diameter almost that of passage 54 projecting well into the passage 54 when Vthe plunger is close to the intake en-d of chamber 64. The boss 84 has the effect of smoothing out the movement of the plunger 62 under the pulsations of pressure in the fluid in the chamber 64.

While the arrangement of the alleviator as shown in Fig. 1 and heretofore described in relation to the pump, follows the more usual practice, it has been found expedient, and in some cases desirable, to use the arrangement illustrated in Fig. 3. In this arrangement, it is shown how to permanently close or omit the intake valve 18, to discontinue those portions of pipe 20 which extend below the level of pipe 46, to move the T 50 to the right, connecting pipe 20 in the side port 52, continuing pipe 46 connected to the end port 88, and attaching the alleviator 48 in a horizontal position to end port 86 of T 50. With this arangeinent, the deflecting member 78 can be eliminated since the discharge from the relief valve is directly into the passage 54 of the alleviator, and the relief valve 34, since it is opened during the suction stroke of the pump, Serves the purpose also of an intake valve. Further, it is sometimes preferable to also omit the outlet` valve 22 of the fuel pump since the function of this valve can be sufficiently well performed bythe injection valve 12.

It willbe understood that while we have described herein and illustrated particular embodiments of the present invention, we do not limit ourselves to details of the disclosure, the invention being -deiined and limited solely by the appended claims.

Having thus described our invention, We claim:

l. The combination with a pump having a pressure chamber and intake and relief valves therefor, of a supply line connected to said intake valve, an overflow line connecting said relief valve to said .supply line, an accumulator chamber connected to said overflow line, a plunger in said chamber, means permitting the free flow of fuel into said accumulator chamber from said relief Valve and restricting the flow of fuel from said accumulator to said supply line.

2. A pressure alleviator including a T, an accumulator chamber connected to a passage through said T, a. plunger in said chamber, means for urging .said plunger in a direction to expel iiuid from said chamber through a discharge passage, and a deflector fixed in said T and having its center adjacent said discharge passage of said T and partially obstructing the same.

3. A pressure alleviator including a T, an accumulator chamber connected to a passage through said T, a. plunger in said chamber, means -for urging said plunger in a direction to expel fluid from said chamber, a deflector lixed in said T and having its center toward the discharge side of said T from the center of said T and partially obstructing the discharge therefrom, and a boss projecting from said plunger into the connecting passage between the accumulator chamber and the T.

PERCY BIGMORE LEVITT. THOMAS S. BLAIR. 

